Hot Hide Glue and Vacuum Clamping

Blending “old” tech with “new” tech.

HHG, vacuum clamped in a radius mold.

I'm a bit confused- Is that a laminated back, laminated with HHG in a vacuum bag??

Beau Hannam Ukuleles said:

I'm a bit confused- Is that a laminated back, laminated with HHG in a vacuum bag??

Click to expand...

It's a solid back, with the cross strips glued with hhg, vacuum clamped, in a radius mold. Note how the radius is held by the cross strips, not by a laminated back. I've never done that with Titebond and clamps/go bar/whatever.

Nice- that is very interesting-
When i glue on a (what i call) a marriage strip it basically does nothing to hold shape. I used to use spruce, now i use mahogany veneer, but either way it doesn't do this.
Have you tried the brace that is glued to the middle of the back braces, running from butt to neck to hold the radius??? I wanna try that

You might look at this site....... great press and does work..... (a good friend owns this company) It is pricey but you might get some idea's....and it can be done on your own if you have a mine to do so......(Hide glue will not work, as the time necessary to place pieces and parts into the form take to long)

( a sanding bowl will not work for the form if you use a radius top or back and varying heights at the rear and front of the instrument ....... this form has to be Cad designed and cut on a CNC)

Watch the video...

http://luthiertool.com/vacuum_press.html

I do all my bracing in CNC carved dishes and vacuum press. Using HHG.

For my back reinforcement / marraige strip I most often use the same timber as the back but sometimes spruce. I go with the grain from neck block to tail block instead of cross grain.

I get some arch held in my glue ups, but not to the extent you have here. I'm wondering if it's the cross grain glueup that is helping here?

Allen said:

I do all my bracing in CNC carved dishes and vacuum press. Using HHG.

For my back reinforcement / marraige strip I most often use the same timber as the back but sometimes spruce. I go with the grain from neck block to tail block instead of cross grain.

I get some arch held in my glue ups, but not to the extent you have here. I'm wondering if it's the cross grain glueup that is helping here?

Click to expand...

Not sure if it's the cross grain, but for sure it's the vacuum press AND hhg. I will say this, when the strips with hhg hit the quilted maple back, there's enough water in the glue that actually made the back convex up. I had to press it the opposite direction into the mold, cover it with mesh, then the vacuum bladder. This is the end result.

The shape is easy to maintain with braces, but held in place with just the marriage strips (learned a new term) isn't something I see too often.

Kevin Waldron said:

You might look at this site....... great press and does work..... (a good friend owns this company) It is pricey but you might get some idea's....and it can be done on your own if you have a mine to do so......(Hide glue will not work, as the time necessary to place pieces and parts into the form take to long)

( a sanding bowl will not work for the form if you use a radius top or back and varying heights at the rear and front of the instrument ....... this form has to be Cad designed and cut on a CNC)

Watch the video...

http://luthiertool.com/vacuum_press.html

Click to expand...

My press works the same, based on inserts. I sort of copied Joe Souza's at Kanilea.

I do have to disagree with not using hhg. My experience is vacuum pressing is THE reason to use hhg on braces, which I do for tops and backs. I can't do them all in one pressing, but 2 or 3 doesn't take that long. In theory, I could glue and press a top in 30 minutes- scrap tested- but I don't. Of course, I work in warm weather here, so open time is pretty good.

And Luthier Tools has some cool stuff! That self aligning binding cutter! I'm fabricating a version of it in my mind (got the bearings) that uses a zero bar, which I've grown used to. Tell them to make one with the bar!

With the braces in, the cross radius is expected. Top to bottom is still held by the marriage strips.